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A Level Physics > Chapter 6 > Flashcards

Chapter 6 Flashcards

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1
Q

What does the principle of superposition state?

A

That when 2 or more waves overlap (superpose), the resultant displacement at a given instant and position is equal to the sum of the individual displacements at that instant and position.

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2
Q

A wave transfers energy away from [ ]

A

Its source

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3
Q

A progressive (moving) wave carries [ ] and usually information from one place to another without transferring any [ ]

A

Energy

Material

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4
Q

How can you tell that EM waves carry energy?

A

They heat things

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5
Q

How can you tell that X-rays and Gamma rays carry energy?

A

They knock electrons out of their orbits, causing ionisation

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6
Q

How can you tell that sound waves carry energy?

A

They cause things to vibrate

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7
Q

How can you tell that water waves carry energy?

A

Wave power can be used to generate electricity

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8
Q

Since waves carry energy, the source of the wave [ ]

A

Loses energy

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9
Q

Define Displacement (X, m)

A

How far a point on the wave has moved from its undisturbed position

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10
Q

Define Amplitude (a, m)

A

Maximum displacement

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11
Q

Define Wavelength (λ, m)

A

The length of one whole wave

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12
Q

Define Period (T, s)

A

The time taken for a whole vibration

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13
Q

Define Frequency (f, Hz)

A

The number of vibrations per second passing a given point

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14
Q

Define phase difference

A

The amount by which one wave lags behind another wave (degrees or radians

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15
Q

What is intensity?

A

The rate of slow of energy per unit area perpendicular to the direction of travel of the wave

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16
Q

Equation for intensity

A

Intensity (I, Wm⁻²) = Power (P, W) / Area (A, M²)

17
Q

When does superposition happen?

A

When 2 or more waves pass through each other

18
Q

Superposition: What happens at the instant the waves cross?

A

The displacements due to each wave combine

19
Q

The principle of superposition:

A

When 2 or more waves cross, the resultant displacement = the vector sum of the individual displacements

20
Q

Interference can be [ ] or [ ]

A

Constructive or Destructive

21
Q

What is total destructive interference?

A

When a peak and a trough are of equal size and they completely cancel each other out

22
Q

When is destructive interference not total?

A

When the waves are not the same size

23
Q

What are the arrows called, that represent wave superposition?

A

Phasors

24
Q

In [ ] means in step

A

Phase

25
Q

2 points on a wave are in phase if they are both at the [ ] in the [ ].

A

same point

wave cycle

26
Q

360° = ? Radians

A

2π Radians

27
Q

Describe the waves that are in phase

A

Points that have a phase difference of 0 or a multiple of 360° are in phase. Their phasors point in the same direction.

28
Q

Describe the waves that are in anti-phase

A

Points with a phase difference of odd-number multiples of 180°. Their phasors point in opposite directions.

29
Q

To get interference patterns the 2 sources must be [ ]

A

Coherent

30
Q

Define coherent

A

2 waves are coherent if they have the same wavelength and frequency and a fixed phase difference between them

31
Q

Define path difference:

A

The amount by which the path travelled by one wave is linger than the path travelled by the other wave

32
Q

Describe the situation where you will get constructive interference from 2 waves

A

At any point an equal distance from both sources (coherant and in phas) or where the path difference os a whole number of wavelengths
Path difference = nλ

33
Q

Describe the situation where you will get total destructive interference from 2 waves

A

At any point where the path difference is an odd number of half wavelengths
Path difference = (2n+1)λ / 2 = (n + 1/2) λ

A Level Physics (22 decks)

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